The present invention relates to locksets in general, and more in particular to double bolt locksets.
Locksets for the security of habitated and other space have taken a variety of forms. One form provides a key in a knob. This type of lockset is extremely convenient. It has a spring latch bolt biased to an extended position so that upon closing a door, the door stays shut without more. The latch bolt can be locked to lock the door. However, the security of the lockset is low. The projection of the latch bolt is short and therefore springing the door or door jamb to release the latch is a distinct possibility. This lockset also suffers because it breaks easily. For example, the knob can be pried off with a tube, exposing the latch to easy retraction.
A second type of lock is a mortise lock. These locks are considerably less vulnerable and are of much stronger construction than key-in-the-knob locks, but they too have fallen into disfavor in recent years. A mortise lock requires a large cutout space in the door to receive a large lock case that contains the lock mechanisms. The space weakens the door. A good swift kick near the lock can often split the door and permit entry. Mortise locks are also expensive to install and to make.
A third type of lock is the deadbolt lock. A deadbolt may be extended and retracted with a key from the outside, and the likes of a thumb turn from the inside. If this lock is well constructed, it can offer the best security of any of the locks discussed here. The deadbolt lock does not require the large cutout space that a mortise lock requires and can provide a bolt that projects substantially for cooperation with a deep hole associated with the door jamb. The difficulty with deadbolts is that they require the use of a spring latch bolt to retain the door closed when the deadbolt is retracted and the door is unlocked.
Notwithstanding this defect in deadbolts, in recent years it has been the trend to construct locksets by combining both a deadbolt and a spring latch bolt. Some of these constructions have the deadbolt only locking. Others lock both the deadbolt and the latch bolt. Clearly, when a latch bolt locks, it is necessary to provide some mechanism for this purpose, such as a cylinder, pusher turn button, or the like.
Obviously, there is substantial inconvenience in a double locking lockset in having to independently unlock both the latch bolt and a deadbolt. Some constructions employing both a deadbolt and a latch bolt simultaneously retract both the deadbbolt and the latch bolt by actuation of a single inside operator, such as an inside knob.
U.S. Pat. No. 3,910,613 to Roger Nolin describes an elegantly simple lock that permits the simultaneous opening of a spring latch and deadbolt in a surface-mounted lockset. But the patent does not describe a simultaneously locking and unlocking latch bolt and deadbolt.
Simultaneous locking and unlocking locksets have been found in mortise-type locks, such as shown in U.S. Pat. No. 3,337,248 to Fred J. Russell and Roger J. Nolin. In mortise-type locks all the components, the deadbolt mechanisms, latch bolt mechanisms, key mechanisms, and retracting mechanisms, are located in the same case in close proximity to each other. Accordingly, it is comparatively easy to arrange the components at will. Even with the attraction of mortise-type locks in the ability to simultaneously lock and unlock both a deadbolt and a latch bolt, these locks still offer poor security, and suffer because of high installation and construction cost.
It has also been recognized that locksets providing a panic proof exit capability are highly desirable. This type of lockset retracts both a lock bolt and a latch bolt with a single operation on the inside of a door. U.S. Pat. No. 3,910,613 referenced above is an example of such a panic proof lockset.
U.S. Pat. No. 3,791,180 to William J. Doyle illustrates a different construction for a panic proof lockset in a surface-mounted lockset. This construction uses a gear sector to interconnect deadbolt and latch bolt assemblies. The construction shows separately keyed lock bolts and latch bolts. Doyle does not provide for simultaneous locking and unlocking of both a deadbolt and a latch bolt with but a single operation from either inside or outside of a door.
U.S. Pat. No. 3,390,558 to Torno et al shows a complicated lock having many desirable features. It is panic proof and has a latch bolt and deadbolt that can be simultaneously opened from either inside or outside of a door. This construction, however, does not provide a lockset that has a latch bolt and a deadbolt that simultaneously lock or unlock.
The latch bolt is independently locked with push turn bottom on the face of the inside knob. Turning the outside key retracts the deadbolt and the latch bolt, but the latch bolt remains locked. The control on the knob face has to be manually operated to unlock the latch.